1. Field of the Invention
This invention relates to improved corrugated steel floor decking sections of the type which are used to construct floors of modern buildings.
2. Description of the Prior Art
Corrugated steel floor decking has been employed as a construction component for buildings for many years. The corrugated steel floor decking is fastened to the steel framework of a building and constitutes a membrane surface of each floor of a building and serves as a permanent form for subsequently applied concrete. Throughout the life of the building the concrete serves as the walking surface for each floor. In the early building construction days, the steel floor decking served merely to support and shape the wet concrete until it was hardened; consequently the steel decking was not considered as contributing to the strength of the resulting building floor.
Subsequently, variations in the surfaces and profiles of the steel floor decking section permitted the interengagement of concrete and the steel decking section whereby the concrete and steel acted compositely in the resulting building floor. The steel floor decking could be taken into consideration for its contribution as a tensile stress-resisting component and the concrete could be employed for its compressive stress-resisting characteristics. In such composite floor buildings, both the concrete and steel contribute to the ultimate load carrying capability of the building floor.
In order to combine the steel and the concrete as described, indentations, embossments, grooves, ribs and other physical deformations of the corrugated steel decking have been introduced to achieve mechanical interferences with the subsequently poured wet concrete and thereby to assure a positive bonding between the steel decking and the hardened concrete.
All of the prior art composite steel floor decking sections experience a number of shortcomings.
Any composite steel decking experiences three distinct phases of its life history. In the first phase of the life history of the steel decking, the decking is secured to a structural building framework, usually horizontal steel beams which extend between vertical steel columns. The decking sections are assembled in side-by-side relation and engaged with lateral connecting means. The decking sections are secured, usually by welding, to the horizontal beams and serve as a walking surface for various trades in the building construction prior to the pouring of wet concrete on top of the assembled decking sections to establish the building floor. During this first phase, the steel decking sections constitute the only available structural component upon which workmen may walk and move construction vehicles. The steel decking must possess sufficient strength to support the weight of the workmen and anticipated construction traffic.
During the first phase, while the steel decking is in position and before the wet concrete has been poured, the prior art steel decking is susceptible to serious damage which may result from localized impact loads when workmen tread heavily upon corners of the decking or when workmen drop heavy construction tools on the decking.
In the second phase of the lifetime of the steel decking, wet concrete is poured over the entire surface of each floor. The wet concrete makes no contribution to the load-carrying capability of the resulting floor. Accordingly, during the second phase of its lifetime, the steel decking must carry not only its own weight but also the weight of the wet concrete. The ability of steel decking to sustain the load of wet concrete has been characterized as the "wet strength" of the decking. Where the "wet strength" of the decking is inadequate to sustain the weight of wet concrete over the span, it is customary to provide props or shoring to supplement the load-carrying capability of the decking. The inconvenience and expense of such shoring has been a serious shortcoming of many prior art steel decking sections.
The third phase of the life of the steel decking commences after the wet concrete has hardened and the hardened concrete is combined with the steel decking as a composite floor structure. During this third phase, a good mechanical bond exists between the hardened concrete and the steel decking.